“At the moment it’s something we need to watch but not fear,” says Nariman Behravesh, chief economist at IHS, Inc., an economic research company in Lexington, Mass. “The US is growing almost three times as fast as Europe and the biggest impact is likely to be as Europe grows slowly, our exports to them grow slowly.”

The actual impact of this slower growth and fewer tourists walking around the US will be relatively small but measurable, says Mr. Behravesh. “If we’re growing at 3 percent, it could take a couple of tenths off our growth,” he says.

All US exports represent about 11 percent of US gross domestic product (GDP). Of those, 20 percent go to Europe. So, about 2 percent of the nation’s GDP is involved in exports to Europe.

“Any reduction in exports is not a good thing, but it probably won’t drive the US back into a recession,” says Mr. Bryson.

But, at the same time as some European nations have to tighten their belts, the European Union may have to mount a massive bailout of European banks that own much of the downgraded sovereign debt. Behravesh estimates it could cost as much as €600 billion ($800 billion) to rescue the banks.

Greek bailout not a sure thing

If the Europeans are going to bailout Greece, a lot of the money will have to come from Germany, where public polls indicate opposition to the rescue. “It’s not a sure thing,” says Bryson. “It may not get done.”

And, as other economists point out, throwing money at Greece might be just the first step.

“The problem, of course, is that if Greece is bailed out, then surely Portugal, Ireland, Spain, and perhaps even Italy may not be too far behind,” writes David Rosenberg, chief economist at Gluskin Sheff, a Canadian wealth management company, in a report.

In the case of Spain, he writes, the amount of debt it has to refinance in the coming year is as large as the Greek economy. “So this is not even a case of being too big to fail as much as being too interconnected globally to default,” he concludes.

Exactly how much Spanish debt is on the books of the US banks is not clear. But Behravesh does not think it presents a major risk to the US banking system.

“There is always the risk to individual banks,” he says. “But it does not present a systemic risk to the US.”